Desiccants are widely used in connection with hygroscopic chemicals to prevent or retard the problem of degradation of these chemicals. Typically the problem is solved by building very expensive humidity controlled rooms in which tablets or powders are packaged into vials which are then sealed against moisture. The problem may also be solved by providing a desiccant canister which is permanently open to expose it to the surrounding air in a vial containing tablets. The canister itself must be protected from moisture until it is placed in the vial either at a packaging facility or at the pharmacy. The desiccant could also be incorporated into the closure (lid) such as is done in the U.S. with certain chemicals. This method is widely used in Europe for effervescent products using friction-type closures. In either case, the desiccant can become separated from the product, exposing the product to moisture. The desiccant itself, prior to use, must be carefully packaged to avoid moisture exposure that would diminish its effectiveness.
DE 3,622,773 discloses a plastic stopper closure with a dryer insert that may be pressed into the opening of a container such as a tube or bottle. This stopper seals to the inner surface of the container and is filled with a drying agent which is held in place by a disk. DD 148,749 discloses a plastic closure for medication bottles consisting of a hollow elastic stopper containing an elastic telescoping insert filled with stabilizer.